304 ECTOPROCTA. 



itself, dilates into a stomach, and is continued parallel to the 

 oesophagus as the rectum which opens by an anus (a 1 ) at the 

 posterior end of the vestibule. A peculiar paired organ is 

 situated on each side nearly above the stomach. Its nature 

 is somewhat doubtful. It was regarded as muscular by Clapa- 

 rede (No. 309), though this, as shewn by Schneider, is no doubt 

 a mistake. Allman (No. 305) regards it as hepatic, and Hat- 

 schek as a thickening of the epidermis. Close to each of these 

 organs is a small body regarded by Claparede as an accessory 

 muscle. It is placed in the normal position for a Polyzoon 

 ganglion, and may perhaps be therefore regarded as nervous in 

 nature. Allman points out its similarity to a bilobed ganglion, 

 but is not inclined to take this view of it. The constitution 

 of the parts contained in the anterior cavity (x) is somewhat 

 obscure. The most elaborate descriptions of them are given by 

 Schneider and Allman. Lining the cavity is apparently a mass 

 of spherical bodies, connected with which is a tongue-like process 

 provided with long cilia, which can be protruded from the orifice. 

 Internal to this is a striated body. A good figure of the whole 

 structure is given by Schneider. 



The general similarity of Cyphonautes to the other larvae is 

 quite obvious from the above description and figure. In the 

 presence of an anus, a vestibule, and possibly a nervous 

 system, it clearly exhibits a far more complicated organisa- 

 tion than any other Polyzoon larvae except those of the 

 Entoprocta. 



The post-embryonic metamorphosis of Cyphonautes, ad- 

 mirably investigated by Schneider, takes place in the same 

 manner as that of other larvae, and is accompanied by the de- 

 generation of the larval organs, and the formation of a clear 

 body, which gives rise to the alimentary cavity and lophophore 

 of the fixed polype. The larval shell takes part in the formation 

 of the ectocyst of the polype. 



Cyclostomata. We owe to Barrois by far the fullest account of the 

 development of the Cyclostomata, but how far his interpretations are to be 

 trusted is very doubtful. The larvae differ very considerably from the 

 normal larvae of the Chilostomata and Ctenostomata ; the difference being 

 mainly due to the enormous development of the ciliated disc. Barrois has 

 investigated the larvae of three genera, Phalangella, Crisia, and Diastopora, 



